Apparatus for reducing precious metals



Jan. 25, 1955 H. w. DORMAN 2,700,457

APPARATUS FOR REDUCING PRECIOUS METALS Filed May l1, 1953 2 Sheets-Sheet 2 b un* I l N E IN VEN TOR.

Harry M/.or/Wan yf@ /W United States Patent The present invention is apparatus for reducing precious metals fromore.

.One object of thezinvention lies. inthe provision of an ,'apparatusadapted to reduceiprecious metals having an laffinity for mercury .by meansof centrifugal` force.

Anotherobject of-the.invention lies in the ,provision of ya centrifuge having nmercury 'therein `and adapted to :receivepulverizedoresuspended in a liquid carrler whereby `the preciousmetal isV drivenby centrifugalforce into .the mercury to form an amalgam.

Anotheriobjectvv ofthe invention` is to provide.l means to reduce precious metals havingan a'flinityfor mercury :by kutilizing .,:a .compartmented centrifuge v.containing rmercury.

`,Another object ofztheiinvention `lies.in the .provision of .an apparatus forfreducingsprecious metalswhich comprises a pair of centrifuges which may beindependently rotated at selectivezspeeds to completely separatethe precious. metals in. orel anda having. an afnity for.v mercury.

Thesetan'd otherobjects of the? invention will becomeapparentduring 1 the course-` of the; following description.

In the accompanying drawings, forming a part of this specicationgandl. inwwlichrlike numerals; areeemployed to designate like, parts;

Figure 1 is a side elevation showing al physical embodimentof the present, invention;

'-Figure 2is alongitudinalcross section takenithrough the first centrifuge;

Figure 3 is a transverse cross section taken atline 3 3 Aof'Figurel;

Figure 4 is a transverse cross 4-4 of Figure 2;

Figure 5 is a fragmentary enlarged transverse cross section through a wall section of the rst centrifuge;

Figure 6 is a longitudinal vertical cross section of a modified tube adapted to be contained within the housing of the first centrifuge;

Figure 7 is a longitudinal vertical cross section taken through the second centrifuge;

Figure 8 is a transverse cross section of the same; and

Figure 9 is a View partially in longitudinal cross section showing an inlet pipe.

Referring now more particularly to the drawings, I have shown a pair of spaced centrifuges 10 and 11 which form parts of the separator and are applicable to the practice of the present process. The centrifuges are not identical and the one indicated by the numeral 10 Will be termed the first centrifuge and the one designated by the numeral 11 will be termed the second, since the pulp advances into the first centrifuge and thence the second.

In the disclosure, the centrifuges are disposed in axial alignment with their axes on a horizontal plane. It will be understood, however, that the axis of each centrifuge may be vertically disposed if desired and they need not be axially aligned to function properly.

The rst centrifuge 10 comprises an elongated cylinder 12 having outwardly disposed annular flanges 13 at each end. The cylinder may be made of any suitable material but for reasons of structural support, I am presently employing steel. The cylinder is formed of two semicylindrical sections 14 having longitudinally extending flanges 15 along their marginal edges and companion flanges 15 are secured together by means of bolt and nut units 16.

Within the cylinder 12 of the first centrifuge, I have provided a tubular sleeve 17 which has a silver inner lsection taken at line nf' ICC 2 face -118 :and maybe `ofLany'- desired material, adequate to support the face. Presently,'the body 'of sleeve' 17 is copper-with `a-:silver platev on its inner face. f Outwardly 4extending annular flanges=19 are carried atI the open-ends Lof the sleeve 17. .Intermediate the length-ofl the sleeve 17 I have .provided an .inwardly disposed annular-ribl20 :which divides thecentrifuge `into compartments. -The receiving compartment/21m the forward endof .thelsleeve .17. is internally coatedwithmercury. as at '.22 of Figure'S. vThe `mercury,.ha\'fing an affinity forzsilverfwill adhere? to the surfacethereofland form a cushion or coatingy thereon. If `desired,ffree mercury may also be-tintroduced: into .the firstcompartment, that i'srmore mercury thanwill normally adhere tof the .side '-wa'lls of the-sleeve, butqnotlin quantities great'enough2to overflow-rib 20into th'e.dis charge compartment v3.4.

Theends ofthe'cylinder 12` and sleeve17vare .closed by means of tapered 1 end caps Y23-which have `annular flanges `24 adapting `.themto be'bolted byzmeans of lbolt and nut units lf25fto the? flanges 13 ofthe cy1inders12 with the vflanges 19 clampedtherebetween. iThe endcaps'23 .are provided l with; circumferentially extending'v sleeves 27 and these sleeves arey adapted to receive/the inlet andg'outlet pipes..28 and 29. `As indicated,the-sleevesmay bev secured about the rpipes T28A and' 29. Howeven,y it 'will "be un'derstoodthat suitable fluid l"tightlb'earings may-"betinvcorporated in' the sleeves andi the pipes 528r andi'29 ymay; be `stationary twhile' the centrifuge isa'dapted for'rota't'ionpif found: desirable.

In :the .event lit `is fdesired. to provide a restrict-ing ridge, plane collar.2.6 f may' .also l be `clamped lintermediate .the'ilanges 224 `an'cl `16.' and its central.' aperture mayl'be of any desired size to provide a ridgerof-the height-desired.

=Theii1nlet pipe28-communicates: an. agitatingf-tankI (not shown) 2 to fthe interior of' the` receiving' compartmentzl land lthe pipe is :pro/vided with :radial Vslotsvl301andsend plate 31 which causethe Ainflowingtpulp` tofbedischarged radially. from the.I pipe toward'` the mercury: coated. armu- `la`r:inner1wallof the receiving'compartment!21. i

In the present disclosed embodiment ofthe-invention, pulleysZware .secured Vto the inlet; pipe 128 whichy is carried in: a 'bankz of :selfaaligned bear-ings `33:.an`da\.suitable f r'o- .tatingsource lof; power. ('fnot shown) isbeltedto the pulleys i tol' impart lrotary 'movement-'101 the; 'centrifuges 1.1101and The speed of rotation of the centrifuge 10 need be only sufficiently fast to cause the elements having a specific gravity of 13 or more to hold to the annular face of the compartment 21. It will thus be seen that elements such as gold, mercury and platinum will adhere to the surface and be amalgamated with the mercury while the lighter elements, by means of the flow of the pulp from the receiving agitator tank out through the discharge pipe 29, will be discharged from the centrifuge. The speed of rotation will vary according to the diameter of the compartment 21 and according to the elements to be separated. Greater speeds may be employed if desired and the separation will be adequately accomplished. Theoretically, the speed of an l8-inch diameter receiving compartment could be increased to 4000 R. P. M. However, at this speed, it is found that the lighter pulverized materials such kas rock, iron, etc., are inclined to cake upon the walls and interfere with the amalgamation of the precious metals and the mercury. At such speeds, however, the slight difference in weight distribution of the centrifuge sets up suicient vibration to adequately dislodge the packed elements and permit the heavier elements to amalgamate with the mercury. Obviously, for reasons of operational costs and machine wear, it is contemplated rotating the centrifuge at much slower rates of speed, even as low as 300 R. P. M., and even though I have not conducted actual experiments at speeds lower giag l/ilis, theoretically, it will operate at somewhat less In practice, it is found that the talc and other finely pulverized elements which are not amalgamable with mercury will form a tough skin over the surface of the mercury and this causes the mercury to flake or our off in very minute quantities and be carried by the advancing pulp into the second or discharge compartment 34. The

' mercury, having a greater specific gravity than most of the k-nown elements, will be disposed on the silver lining ofthe discharge compartment 34. In the event any of this mercury should pass the barrier 26 and enter the discharge pipe 29, it will be again separated and recovered in the second centrifuge 11.

' Within the Vvinlet pipe 28, it is desirable to provide an Aagitatorwhich will maintain the pulverized ore in suspension `in the vehicle fluid. To accomplish this, I have provided a spiral 35 which may be rotated to advance the pulp through the pipe 28 and simultaneously agitate the material sufficiently to maintain the ore in suspension. Also the spiral may be fixed within the pipe and when the pipe is being rotated at high speed, the pulp is advanced by means of rotation of the spiral.

,In the second centrifuge 11, I utilize an identical housing which comprises the cylinder 12 formed from semicylindrical sections 14 having flanges 15 bolted at 16 and supplied with end caps 23. This centrifuge is provided also with pulleys 32 and bearings 33 and an inlet pipe 36 which is adapted to receive the outlet pipe 29 carried in a bearing 33 and communicate the two centrifuges.

The inlet pipe is provided with radially disposed slots 30 and an end plate 31 and may be of the type shown in Figure 2 or be provided with a separate cap 31', as shown in Figure 9, threadedly engaged to the end of the inlet pipe as 28 or 36.

Within the cylinder 11, I provide a fabric sleeve 37 which may be of burlap or corduroy and within this sleeve is a wire mesh cylinder 38. The wire mesh cylinder is provided with a spiral ange 39 on its inner face and designed to advance the pulp entering the second centrifuge therethrough and discharge it through discharge pipe 29. Any mercury or heavy precious metal whichimay, by chance, pass from the lirst centrifuge will thus, by centrifugal force, be deposited in the fabric 37 from whence it may later be removed.

As shown in Figure 6, I have provided a modified sleeve 17 and, instead of having the circumferentially eX- tending inwardly disposed ridge 20, I provide a spirally disposed ridge which, it is anticipated, will advance the pulp through the sleeve 17. In this modified construction the complete inner face of the sleeve will be coated with mercury.

In practicing the disclosed invention, I iirst pass the mined ore in dry form through a primary crusher where it is reduced to approximately one-half inch mesh. The product is then reduced to approximately 40 mesh through a secondary wet grinder and is subsequently pulverized to from to 300 mesh and suspended in a liquid carrier which may be water. During this pulverizing process, I introduce suiicient cyanide to place the free gold in solution and introduce the product into an agitating tank which maintains the suspension of the particles and solution of the gold and, after agitation for a suitable length of time, say 16 hours, a valve is opened and the solution is permitted to ow freelythrgh the inlet pipe 28 into the centrifuge where the previously described process is effected and separates theparticles of metals from the pulp arnalgamating the metals having an ainity for mercury therein. After completion of the separation, the cylinders 1t) and 11 are opened and the sleeves 17 and 37 are removed, the amalgam is scraped from the sleeve 17 and the preciousmetals are reduced in a conventional retort. The mercury and amalgam is removed from the fabric sleeve 37 and also separated in a conventional retort, and the mercury is thus saved and re-used innumerable times. Y

Having thus described my invention, I claim:

l. A centrifugal separator comprising an elongate cylinder having semicylindrical sections releasably united; an annular sleeve disposed within the cylinder; said sleeve having an inwardly disposed annular ridge defining-compartments; mercury coating the inner face of said'sleeve; outwardly extending annular flanges on the marginal` ends of said cylinder and sleeve; end caps secured in closing relation to the ends of the cylinder and clamping said flanges; and inlet and outlet pipes communicating with the cylinder through said end caps.

2. A centrifugal separator as dened in claim 1 wherein the inlet pipe is provided with radially disposed discharge slots positioned Within the first compartment of said sleeve and having a cap closing the open end of said inlet pipe.

3. A centrifugal separator comprising a pair of intercommunicating centrifuges, one containing mercury for amalgamation and the other containing a fabric sleeve for confining amalgam escaped from the rst centrifuge.

References Cited in the ile of this patent UNITED STATES PATENTS 969,591 Abeel Sept. 6, 1910 1,603,125 Lewis Oct. 12, 1926 FOREIGN PATENTS 794 Australia of 1931 

1. A CENTRIFUGAL SEPARATOR COMPRISING AN ELONGATED CYLINDER HAVING SEMICYLINDRICAL SECTIONS RELEASABLY UNITED; AN ANNULAR SLEEVE DISPOSED WITHIN THE CYLINDER; SAID SLEEVE HAVING AN INWARDLY DISPOSED ANNULAR RIDGE DEFINING COMPARTMENTS; MERCURY COATING THE INNER FACE OF SAID SLEEVE; OUTWARDLY EXTENDING ANNULAR FLANGES ON THE MARGINAL ENDS OF SAID CYLINDER AND SLEEVE; END CAPS SECURED IN CLOSING RELATION TO THE ENDS OF THE CYLINDER AND CLAMPING SAID FLANGES; AND INLET AND OUTLET PIPES COMMUNICATING WITH THE CYLINDER THROUGH SAID END CAPS.
 3. A CENTRIFUGAL SEPARATOR COMPRISING A PAIR OF INTERCOMMUNICATING CENTRIFUGES, ONE CONTAINING MERCURY FOR AMALGAMATION AND THE OTHER CONTAINING A FABRIC SLEEVE FOR CONFINING AMALGAM ESCAPED FROM THE FIRST CENTRIFUGE. 